Fatty alcohols have many commercial uses as components of industrial agents and processes, particularly in the production of detergents and surfactants. They are used as emulsifiers, emollients and thickeners in cosmetics and foods and as industrial solvents and plasticizers. Fatty alcohols can be produced from petrochemical- or oleochemical derived feedstocks. Petrochemicals are chemical products derived from petroleum. Oleochemicals are refined oils derived from natural sources such as plant and animal fats.
The chemical route for making fatty alcohols is energy intensive and environmentally costly and requires the use of hazardous reagents. For example, ethylene can be oligomerized using triethylaluminium followed by air oxidation. This process creates even-numbered fatty alcohols and is known as the Ziegler process. Alternatively, ethylene can be oligomerized to give mixtures of alkenes, which are then subjected to hydroformylation, resulting in odd-numbered aldehydes that are subsequently hydrogenated to give fatty alcohols. In another chemical process, olefin products are converted to fatty aldehydes and then to fatty alcohols. The olefin products are made by the Shell higher olefin process that was commercialized in 1977 by Royal Dutch Shell (e.g., producing approximately over one million tons of olefins annually).
The natural route for making fatty alcohols, while considered a green process, is still costly in comparison to the chemical route. Traditionally, fatty alcohols were derived from fatty esters or wax esters, which were originally extracted from the sperm oil of whales and later from tallow (e.g., animal fat from beef or lamb). An alternative plant source for wax esters is the jojoba plant. Today, fatty alcohols can also be produced from oleochemical derived feedstocks (e.g., refined plant oils) such as rapeseed oil, mustard seed oil, coconut oil, or palm kernel oil. Such vegetable oils are predominantly composed of triacylglycerols (TAGs), which contain glycerol esterified with three fatty acids (FAs). The diverse uses of vegetable oils depend on the FA composition of TAG. For example, a high proportion of lauric acid (12:0) is needed for soap production, whereas oils rich in oleic acid (18:1) are recommended for cooking. TAGs can be subjected to transesterification to give esters, which in turn are hydrogenated to fatty alcohols. Although tallow is mostly C16-C18, the chain length from plant sources are more variable (e.g., C6-C24). Long-chain alcohols (e.g., C20-C22) can be obtained from rapeseed or mustard seed while mid-cut fatty alcohols (e.g., C12-C14) can be obtained from coconut or palm kernel oil. Coconut and palm kernal oil are rich in lauric acid (C12) and myristic acid (C14). Since the European outbreak of bovine spongiform encephalopathy (i.e., mad cow disease) in 2000, tallow is commonly replaced by vegetable oleic fatty acids, derived from palm oil and soybean oil.
Fatty diols or aliphatic diols are examples of fatty alcohols and can be produced via chemical methods. For example, 1,3-diols can be synthesized from ethylene and carboxylic acid chlorides (see, e.g., Kirchanov et al. (1981) Translation from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya 4:909-911). 1,3-diols can also be made by hydration of α,β-unsaturated ketones and aldehydes, wherein the resulting keto-alcohol is hydrogenated. Another chemical synthesis of 1,3-diols involves the hydroformylation of epoxides followed by hydrogenation of the aldehyde (e.g., making 1,3-propanediol from ethylene oxide). More specialized routes to 1,3-diols include the reaction between an alkene and a formaldehyde and the use of β-hydroxy ketones. 1,3-diols have been associated with being useful as food additives (see, e.g., U.S. Pat. No. 3,806,615). The 1,3-dihydroxy configuration is responsible for the non-toxic nature of these chemical entities.
1,3 diols are bifunctional, and can be used as linking molecules between other molecules, for example in the production of polymers. For example, a 1,3 propane diol is used as a monomer in the production of polymers. A 1,3 fatty diol can also be used as precursor to surfactants, for example, a “Gemini” surfactant in which both alcohol moieties are chemically modified (e.g., ethoxylated, glycosylated, sulfated, etc.). The 3-hydroxy moieties of 1,3-fatty diols are also chiral, which makes them useful as synthons for the production of chirally important compounds such as monomers, pharmaceuticals, nutraceuticals, pesticides, herbicides, flavors, fragrances, solvents, and the like.
Since fatty diols are important components of industrial agents and processes it would be desirable to produce them in high enough quantities to meet industry needs while maintaining a lower impact on the environment. The present disclosure addresses this need.